1. Field of the Invention
This invention relates generally to data recording disk drives, such as magnetic recording hard disk drives, and more specifically to such disk drives that experience out-of-plane disk vibration induced by air flow during rotation of the disks.
2. Background of the Invention
Data recording disk drives have a stack of recording disks rotated by a spindle motor, and an actuator that moves the read/write heads across the surfaces of the rotating disks. Each read/write head is formed on an air-bearing slider attached to one end of a suspension. The suspension is attached at its other end to a rigid arm of the actuator and allows the slider to pitch and roll on a bearing of air generated by the rotating disk. The disk drive actuator is typically a rotary voice coil motor (VCM) that moves the actuator arm and the attached suspension and slider generally radially to position the head at the desired track under the control of a servo feedback control system that receives pre-recorded servo position information from the disk. The trend in future disk drives is a continual decrease in the spacing of the concentric data tracks on the disk to increase the data storage density, and a continual increase in the rotational speed of the disk stack to decrease the data transfer time. As storage densities and rotational speeds increase, the ability to position the read/write heads to the proper data tracks and maintain the heads on the data tracks becomes more difficult. As the disk-stack rotational speed increases, air-flow turbulence near the perimeter of the disks increases, which causes axial (out-of-plane) buffeting or vibration of the disks (sometimes misleadingly called disk “flutter”). These vibrations cause track-misregistration (TMR) of the read/write heads and thus errors in reading data from and writing data to the data tracks.
Concurrently filed application Ser. No. 10/956,908, now U.S. Pat. No. 7,012,777 B1, addresses the problem of TMR caused by out-of-plane disk vibration by use of capacitive sensors that sense the axial displacement of the disks. The capacitive sensor associated with the disk surface being accessed for reading or writing of data provides a signal to a feedforward controller that provides a correction to the servo feedback control system to thereby significantly reduce the effect on TMR caused by out-of-plane vibration of the disk. The capacitive sensors are located between the axially-spaced disks near the perimeter of the disk stack and securely mounted to the disk drive housing so that they do not experience vibration.
What is needed is a support structure for the capacitive sensors that can be integrated with a conventional disk drive in a low-cost manner without significant redesign of the disk drive housing.